U.S. Pat. No. 6,400,109 B1, Hans Helmut, discloses a rotor position sensor arrangement for an external-rotor motor in which the rotor position is sensed with the aid of digital Hall sensors.
In this context, each signal change of a signal generated by the digital Hall sensors indicates that a specific rotor position in the region of a change in the detected magnetic field has been reached, as well as the direction in which the change has taken place. A rotor position datum is thus obtained at discrete rotor positions.